The metallic cardiac electrodes and leads used in conventional cardiac stimulation and monitoring devices have always been a problem. They tend to fatigue, corrode, and break. Their physical properties (corrosion, strength, chemical activity, etc.) limit the materials which can be used to titanium, platinum metals, their alloys, to certain stainless steels, and to special structures to limit fatigue (such as spring coils, metal cladding, multiple strands, etc.) With respect to metallic leads, a leaky interface is often produced between the metal and the insulating sheath that surrounds the leads.
The problem of metallic leads has been addressed by applicants' assignee in an effort to provide a pacemaker that is compatible with MRI diagnostic imaging procedures. See copending Ser. Nos. 09/864,944 and 09,865,049, both filed on May 24, 2001, and copending Ser. Nos. 09/885,867 and 09/885,868, both filed on Jun. 20, 2001. In these copending patent applications, the contents of which are fully incorporated herein by this reference, MRI compatible/safe pacemakers are disclosed for both implantable and wearable service. The disclosed pacemakers feature photonic catheters carrying optical signals in lieu of metallic leads carrying electrical signals in order to avoid the dangers associated with MRI-generated electromagnetic fields. Electro-optical and opto-electrical conversion systems are disposed at the proximal and distal ends of the photonic catheters to perform the necessary conversions between electrical and optical signaling modes.
The devices of the copending applications require component housings at the each end of the photonic catheter to house the conversion systems and other components. This not a problem at the proximal end because the main pacemaker enclosure is situated at that location. At the distal end, a micro-miniature housing is required that is preferably no wider than the diameter of the photonic catheter, such that catheter insertion is not hampered. In addition to being small in size, the distal component housing must be hermetically sealed to protect the components therein from patient body fluids. Moreover, it should preferably carry at least one of the electrodes used for cardiac stimulation and/or sensing. It is thus purpose and goal of the present invention to address alternative designs for hermetic component housings designed for implantable service at the distal end of a photonic catheter in a photonic pacemaker system.
The foregoing problems are solved by a hermetic component carrying housing for use with a photonic catheter connected to a photonic pacemaker or other medical system designed for compatibility with Magnetic Resonance Imaging (MRI) procedures. The hermetic housing includes a housing body having a proximal end and a distal end. The body is formed with a hermetically sealed interior for carrying one or more electrical and/or optical components therein. The proximal end of the body is adapted to mount to a distal end of a photonic catheter carrying a fiber optic element or bundle. A hermetic terminal is provided to allow the fiber optic element or bundle to communicate with the body interior. The body can be adapted to mount one or more electrodes designed for delivering or sensing electrical signals to body tissue, or it may be adapted to mount no electrodes. The component housing may be implemented by itself at the distal end of the photonic catheter, or it may be used in conjunction with other housings of like or different construction.